Spectra Logic develops various storage libraries for managing digital information in all forms, providing data storage solutions for long-term digital preservation for business.
If you are planning for implementing Spectra Libraries in your work environment, there are several areas of communication concerns between the Spectra Libraries and the devices, the Host Server, the backup software, as well as the Library’s HBA (Host Bus Adapter) that you need to take into consideration prior to the implementation.
Without proper planning, issues may arise and lead to disruption on daily operations.
There are 3 main areas of communication setup that you need to consider:
•Persistent Binding
•Timeout settings in Backup software and HBA
•Windows 2003 / 2008 Test Unit Ready (TUR) commands
Persistent Binding
Persistent Binding is a zoning method through which the HBA (Host Bus Adapter) assign a permanent SCSI target ID to each device on a Fibre Channel. A target ID is part of the identification information where the Server need to keep track of to ensure proper communication with the devices. Persistent Binding is the accepted zoning method to reliably control device access and data security. Without persistent binding, the Server may re-assign target ID to connected devices and increase the possibility of zoning conflicts and resulted in data corruption.
(A HBA is a circuit board or an integrated circuit adapter that provides I/O processing and physical connectivity between a host system and storage or network devices. HBA is commonly used with storage protocols such as Fibre Channel and Serial-attached SCSI.)
Persistent Binding is a HBA function that allows a subset of targets to be bound between Server and devices. Implemented by a World Wide Node Name (WWNN) or World Wide Port Name (WWPN), persistent binding causes a tape drive’s World Wide Name to be bound to a specific SCSI target ID after the configuration has been set. The target ID remains intact after reboots and hardware configuration changes because the information is preserved. If the tape drive needs to be replaced, the new drive would assumes the WWNN of the old drive because the WWNN for the tape drive is location-dependent with the library.
The advantage of Persistent Binding:
•A second Server may use a different SCSI target ID, you can use Persistent Binding to maintain a consistent target ID across all systems and perform certain network tasks, for example, you can consistently map to a tape library for backup purposes.
•Persistent binding is implemented in the HBA. Configuring a logical route across the network fabric in each adapter does it. This ties the HBA to a particular LUN. While the administrator can easily specify storage resources in a multi-host fabric, persistent binding decreases address space and increases network complexity.
Timeout settings in Backup software and HBA
Spectra BlueScale software provide common interface for all Spectra Tape Libraries through the Library’s on-board LCD and remote web access. The interface bundled with several useful utilities and features that ensure Spectra Libraries runs optimally. These features includes Media Lifecycle Management (MLM), Auto Drive Cleaning, Data Encryption, PreScan, PostScan, etc.
You need to take into consideration the “Timeout” settings in both BlueScale software and HBA.
BlueScale:
The timeout settings includes the duration where user interface can be idle before the current user is logged out, resulted the termination of connection to the Spectra Libraries, as well as the timeout set in the Libraries to abort operation tasks in tape library while pending for operator action.
HBA:
The timeout kick-in when operations require I/O process but the Server is unavailable for too long. You need to set a connection timeout for each SCSI HBA to establish the connection.
For both components, Spectra Logic Support recommends setting all timeout to 15 minutes.
Windows 2003 / 2008 Test Unit Ready (TUR) commands
In Windows Server 2003 / 2008, Remote Storage Manager (RSM) keep track of all devices in the storage area network (SAN) by sending SCSI Test Unit Ready (TUR) commands to determine if a device is ready for data transfer (read/write). The commands are sent every second whenever the server is rebooted or when the data transfer application services are enabled. This frequent process enables Device Manager to list devices in Server and enables Windows plug-and-play feature to work. Unfortunately, this process does not function well over a SAN due to commands may conflict with other operations on the Server, as well as disrupt communication and eventually causing the data transfer to fail.
Spectra Logic Support strongly recommends to disable the TUR polling in Windows Server 2003 / 2008 that access to Spectra Libraries and devices for backup operations. You can approach Spectra Logic Support for assistance during the implementation of Spectra Libraries.
Microsoft has three workaround solutions for this problem, two of which require modification to Windows Registry, one is to programmatically disable TUR commands for specific devices. You can refer to Microsoft knowledge base Article #842411 for more information.